4x^2+20x+5y+xy

*you have to factor by grouping,for more information just ask me*

First, take out 4x from the first two and y from the second:
4x(x+5) + y(x+5).
Then combine the 4x and the y:
(4x+y)(x+5).
That's your answer.

thanks. - can you help me with this one?
*48x^2y+20xz+12xy+5z

First, you should notice that 12*4=48 and 5*4 is 20. So, rearrange a little:
12xy + 48x^2y + 5z + 20xz.
Then, take out 12xy from the first two and 5z from the second two:
12xy(4x+1) + 5z(4x+1).j
Combine:
(12xy+5z)(4x+1).

thank you;please help me with my other problems...

Sure, I'd be happy to help you with your other problems. Please provide me with the details of the problems you need assistance with.